Plasma treatment device having matching box

ABSTRACT

Examples of a plasma treatment device include an RF generator, a matching box including an input terminal connected with the RF generator, a sensor configured to sense high-frequency electricity, an impedance adjustment circuit, and an output terminal, a matching controller connected with the sensor and configured to control the impedance adjustment circuit, a reactor chamber connected with the output terminal, and a harmonic filter circuit connected with a transmission line between the sensor and the reactor chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 63/129,542 filed Dec. 22, 2020, thedisclosure of which is hereby incorporated by reference in its entirety.

FIELD

Examples are described which relates to a plasma treatment device.

BACKGROUND

A plasma treatment device generates plasma and provides treatments suchas deposition, etching, and film reforming on a substrate. Harmonicshaving frequencies at integer multiples of that of the fundamental waveare generated from plasma in a reactor chamber. These harmonics affectimpedance matching operation through a matching box in some cases. Whenthe impedance matching operation through the matching box is affected bythe harmonics, increase of reflected wave occurs in a stationary stateduring plasma treatment and a high reflected-wave spike is generated atthe end of plasma treatment in some cases.

SUMMARY

Some examples described herein may address the above-described problems.Some examples described herein may provide a plasma treatment device inwhich influence of harmonic on matching operation is reduced.

In some examples, a plasma treatment device includes an RF generator, amatching box including an input terminal connected with the RFgenerator, a sensor configured to sense high-frequency electricity, animpedance adjustment circuit, and an output terminal, a matchingcontroller connected with the sensor and configured to control theimpedance adjustment circuit, a reactor chamber connected with theoutput terminal, and a harmonic filter circuit connected with atransmission line between the sensor and the reactor chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary configuration of the plasma treatmentdevice;

FIG. 2 shows a circuit diagram of the matching box;

FIG. 3 shows harmonic filter circuits according to another example;

FIG. 4 illustrates the intensity of high-frequency electricity accordingto the comparative example;

FIG. 5 is a timing chart of the plasma treatment according to thecomparative example;

FIG. 6 illustrates the intensity of high-frequency electricity, and

FIG. 7 is a timing chart of the plasma treatment.

DETAILED DESCRIPTION

A plasma treatment device will be described below with reference to theaccompanying drawings. Components identical or corresponding to eachother are denoted by an identical reference sign, and duplicatedescription thereof will be omitted in some cases.

Embodiment

FIG. 1 is a diagram illustrating an exemplary configuration of theplasma treatment device. The plasma treatment device includes, forexample, an RF generator 14 provided in a rack 12. In an example, the RFgenerator 14 outputs two kinds of high-frequency electricity havingfrequencies different from each other. For example, the RF generator 14outputs first high-frequency electricity of 27 MHz or higher and secondhigh-frequency electricity of 430 KHz or lower. In this example, thesekinds of high-frequency electricity are superimposed and provided to areactor chamber through one path. The frequency of the firsthigh-frequency electricity is, for example, 27.12 MHz, and the frequencyof the second high-frequency electricity is, for example, 400 KHz or 430KHz. In another example, the RF generator 14 outputs a firsthigh-frequency electricity of 1 GHz or higher, and a secondhigh-frequency electricity of a frequency lower than the frequency ofthe first high-frequency electricity.

In another example, the RF generator 14 outputs high-frequencyelectricity of one frequency. For example, the RF generator outputshigh-frequency electricity of 27 MHz or higher, or high-frequencyelectricity of 1 GHz or higher.

The power of high-frequency electricity output from the RF generator 14is, for example, equal to or higher than 3 kW. In another example, otherhigh-frequency electricity power may be employed.

The RF generator 14 is connected with an input terminal 18 a of amatching box 18. A matching controller 20 is connected with the matchingbox 18. The matching controller 20 generates a signal for adjusting theimpedance of the matching box 18 and transmits the signal to thematching box 18.

The matching box 18 has an output terminal 18 e connected with a reactorchamber 22. The reactor chamber 22 is a device that stores a substrateas a treatment object and performs plasma treatment on the substrate.

The RF generator 14 is connected with a computer 24, and the computer 24is connected with a man-machine interface (MMI) 26. The computer 24 andthe MMI 26 provide a monitor signal of the RF generator 14 to a customerhost computer. For example, information such as traveling wave power andreflected wave power of the RF generator 14 is provided to the customerhost computer through the computer 24 and the MMI 26. For example, theMMI 26 generates a waveform as illustrated in FIGS. 5 and 7 and providesthe waveform to the customer host computer, and displays theinstantaneous values of traveling wave power, reflected wave power, andthe like. In addition to the RF power information, various kinds ofinformation for monitoring the RF generator 14 may be provided to thecustomer host computer.

The above-described components are provided as a main frame 16.

FIG. 2 is a circuit diagram illustrating an exemplary configuration ofthe matching box 18. In an example, the matching box 18 includes theinput terminal 18 a, a sensor 18 b, harmonic filter circuits F1 and F2,an impedance adjustment circuit 18A, and the output terminal 18 e. Theinput terminal 18 a is connected with the sensor 18 b. The sensor 18 bsenses high-frequency electricity. The sensor 18 b senses, for example,high-frequency electricity of 27.12 MHz. In another example, the sensor18 b senses high-frequency electricity having the frequency of the firsthigh-frequency electricity.

The sensor 18 b is connected with the impedance adjustment circuit 18A.In this example, the impedance adjustment circuit 18A includes variablecapacitors 18 c and 18 d and an inductor L3. The impedance adjustmentcircuit 18A may have another configuration capable of changingimpedance.

The harmonic filter circuits F1 and F2 are connected with a transmissionline connecting the sensor 18 b and the impedance adjustment circuit18A. The harmonic filter circuit F1 is a series circuit of an inductorL1 and a capacitor C1. The harmonic filter circuit F2 is a seriescircuit of an inductor L2 and a capacitor C2. In an example, theharmonic filter circuit F1 is provided to reduce the second harmonic,and the harmonic filter circuit F2 is provided to reduce the thirdharmonic. The harmonic filter circuits F1 and F2 may have cutofffrequencies for reducing the second and third harmonics, respectively.

The kind and intensity of generated harmonic change in accordance withan operation environment such as a process condition, impedance, or thefrequency of high-frequency electricity. Accordingly, the intensities ofthe second and third harmonics are high in an operation environment, theintensities of the second to fourth harmonics are high in anotheroperation environment, and only the intensity of the second harmonic ishigh in yet another operation environment. The harmonic filter circuitsF1 and F2 in FIG. 2 are provided to reduce the second and thirdharmonics, but in another example, harmonic filter circuits may beprovided in an optional number corresponding to harmonics to be reduced.Thus, three or more harmonic filter circuits each including an LC seriescircuit can be provided to attenuate three or more harmonics. Eachharmonic filter circuit includes at least one LC series circuit.

The impedance adjustment circuit 18A is connected with the outputterminal 18 e. The matching box 18 may include a ground terminal 18 fconnected with the reactor chamber 22.

The matching controller 20 is connected with the sensor 18 b describedabove. The matching controller 20 receives a result of detection by thesensor 18 b and controls the impedance adjustment circuit 18A. In thisexample, the matching controller 20 adjusts the capacitance of each ofthe variable capacitors 18 c and 18 d to achieve impedance matching. Forexample, when a variable capacitor, the capacitance of which changes inaccordance with the rotational amount of a rotational axis is used, amotor having received a signal from the matching controller rotates itsrotational axis to adjust the capacitance of the variable capacitor. Themotor may be connected with the matching controller through a signalline and a power source line.

In the example illustrated in FIG. 2, the harmonic filter circuits F1and F2 are provided in the matching box 18. In another example, theharmonic filter circuits F1 and F2 may be provided in a transmissionline connecting the matching box 18 and the reactor chamber 22 asillustrated in FIG. 3. As exemplarily illustrated in FIGS. 2 and 3, eachharmonic filter circuit may be connected at an optional position on atransmission line between the sensor and the reactor chamber.

To clarify the significance of the plasma treatment device according tothe present disclosure, a comparative example will be described below. Aplasma treatment device according to the comparative example has aconfiguration the same as that of the plasma treatment device accordingto the embodiment but without harmonic filter circuits. FIGS. 4 and 5are diagrams illustrating the contents of plasma treatment according tothe comparative example. FIG. 4 is a diagram illustrating the intensityof high-frequency electricity sensed by the matching box in plasmatreatment using the plasma treatment device according to the comparativeexample. FIG. 4 indicates generation of peaks of the fundamental wave of27.12 MHz, the second harmonic, the third harmonic, and the fourthharmonic. FIG. 5 is a timing chart of the plasma treatment in which theharmonics illustrated in FIG. 4 are generated. In this example, twokinds of high-frequency electricity denoted by “RF Forward” and “LRF(Low RF) Forward” are provided from the RF generator, and “RFReflection” and “LRF Reflection” each occur as reflected waveelectricity for the corresponding high-frequency electricity.

In the comparative example, the sensor in the matching box receivesharmonics, and thus matching operation by the matching controller isalso affected by the harmonics. As a result, in the comparative example,reflected wave denoted by “RF Reflection” increases during the plasmatreatment and at the end of the plasma treatment.

FIGS. 6 and 7 are diagrams illustrating the contents of plasma treatmentwhen the plasma treatment device in FIGS. 1 and 2 is used. FIG. 6 is adiagram illustrating the intensity of high-frequency electricity sensedby the matching box. Harmonics moving from the reactor chamber 22 towardthe sensor 18 b are reduced through the harmonic filter circuits F1 andF2, and thus the second and third harmonics are largely attenuated ascompared to the example illustrated in FIG. 4. The reason why the fourthharmonic (108.48 MHz) is hardly detected is thought to be because thefourth harmonic is attenuated together with the third harmonic throughthe harmonic filter circuit F2 for attenuation of the third harmonic.FIG. 7 is a timing chart of plasma treatment in which the harmonics areattenuated as shown in FIG. 6. FIG. 7 indicates that “RF Reflection” isreduced as compared to the example illustrated in FIG. 5.

FIGS. 4 to 7 indicate that a harmonic of high-frequency electricityhaving a high frequency called High-RF (HRF) such as 27.12 MHz is sensedby the sensor 18 b and led to incomplete matching operation. In anexperiment performed by the inventor, the influence of harmonics onmatching operation is large particularly when the HRF is provided at apower of 3 kW or higher.

LRF, which can be superimposed on HRF, also causes harmonic. But suchLRF harmonic causes less real damage than HRF harmonics. Thus, thereduction of “RF Reflection” can be prioritized over the reduction of“LRF Reflection” in FIGS. 5 and 7. Harmonics of high-frequencyelectricity having VHF (very high frequency) in the order of GHz, whichis higher than HRF, cause problems like HRF harmonics. Thus, when VHF isused, as well, harmonic filter circuits through which VHF harmonics areattenuated may be provided between the sensor and the reactor chamber.

1. A plasma treatment device comprising: an RF generator; a matching boxincluding an input terminal connected with the RF generator, a sensorconfigured to sense high-frequency electricity, an impedance adjustmentcircuit, and an output terminal; a matching controller connected withthe sensor and configured to control the impedance adjustment circuit; areactor chamber connected with the output terminal; and a harmonicfilter circuit connected with a transmission line between the sensor andthe reactor chamber.
 2. The plasma treatment device according to claim1, wherein the harmonic filter circuit is provided in the matching box.3. The plasma treatment device according to claim 1, wherein theharmonic filter circuit is provided in a transmission line connectingthe matching box and the reactor chamber.
 4. The plasma treatment deviceaccording to claim 1, wherein the harmonic filter circuit includes atleast one LC series circuit.
 5. The plasma treatment device according toclaim 1, wherein the harmonic filter circuit includes two or more LCseries circuits.
 6. The plasma treatment device according to claim 1,wherein the RF generator outputs two kinds of high-frequency electricityhaving frequencies different from each other.
 7. The plasma treatmentdevice according to claim 6, wherein the RF generator is configured tooutputs first high-frequency electricity of 27 MHz or higher and secondhigh-frequency electricity of 430 KHz or lower.
 8. The plasma treatmentdevice according to claim 6, wherein the RF generator is configured tooutputs first high-frequency electricity of 1 GHz or higher, and secondhigh-frequency electricity having a frequency lower than a frequency ofthe first high-frequency electricity.
 9. The plasma treatment deviceaccording to claim 6, wherein a power of the first high-frequencyelectricity is equal to or higher than 3 kW.
 10. The plasma treatmentdevice according to claim 7, wherein a power of the first high-frequencyelectricity is equal to or higher than 3 kW.
 11. The plasma treatmentdevice according to claim 7, wherein the sensor is configured to senseshigh-frequency electricity having a frequency of the firsthigh-frequency electricity.